STL · P

Riley O'Brien

Age 31 B/T R/R 6′4″, 180 lb USA MLB debut 2021

40-man

St. Louis’ roster as it stands on the 40-man, off the 26-man (call-up depth)
Trade read Available at a price: STL sits near the seller line (27% playoff odds, within a projected win of 30%); control through 2030.

Keystone Stuff 107 76th pct

2026 fWAR 0.3

Projected 2027 WAR 0.2 Keystone Marcel+ at 67 IP

Pitching · 2026 percentiles

vs. MLB pitchers with 500+ pitches · 1,063 pitches

Keystone Stuff 107

Keystone Location 87

Keystone Pitching 96

Run value (xRV) −0.40

Strikeout % 23.2%

Walk % 10.5%

Whiff % 26.5%

Chase % 29.2%

Fastball velo 97.7

Extension 6.8 ft

64.0 IP4.08 ERA3.94 FIP 31° arm38 SV

Arsenal & Pitch Lab

Movement normalized to arm side · Keystone Stuff by pitch

RHP · arm angle 31° · how to read

Pitch	Use	Velo	IVB	HB	Stuff	Loc	Whiff	xRV/100
Sinker58% use	58%	97.7	4.7	+16.1	103	99	16%	−0.55
Sweeper33% use	33%	82.9	−4.4	−14.6	106	81	47%	+0.21
Slider8% use	8%	90.6	3.7	−2.2	105	88	21%	−1.57

No mix change or new pitch clears its bar. The arsenal is efficient for its shapes.

Most similar pitchers

Pitches like O'Brien: same hand, shape, slot and mix

Similarity	Player	Stuff	’26 WAR	’27 proj	2027
58	Colin Holderman CLE · ’95	109	0.8	0.3	Arb
57	Yohan Ramírez PIT · ’95	114	1.2	0.6	Arb
55	Abner Uribe MIL · ’00	113	1.6	1.2	Pre-arb
50	Jordan Hicks CWS · ’96	104	0.5	0.3	Signed $12.5M
48	Spencer Miles TOR · ’00	97	2.0	1.3	Pre-arb

Same-handed pitchers nearest on fastball velocity and shape, arm angle, extension, pitch mix, secondary shapes, Stuff, whiff rate and workload. 2026 regulars only.

Pitch locations · 2026

Where each pitch finishes, by batter side

Sinker 56%

51% zone

Sweeper 31%

25% zone

Slider 12%

51% zone

Where each pitch finishes, catcher’s view. The bar marks the batter’s side; the box is an average strike zone. Pitches with 40+ thrown to this side.

Contract & projection

Club control (RosterResource) · Keystone projected WAR

2027 0.2 WAR Pre-arb $780K*

2028 0.1 WAR Arbitration $1.5M*

2029 −0.1 WAR Arbitration $1.5M*

2030 −0.2 WAR Arbitration $1.5M*

* projected arbitration or minimum salary. Contract Studio →

Minor leagues

MLB Stats API · public box-score data

SeasonLevel	Level	Team	Age	G	PA / IP	PA / IP ·Line
2025AAA	AAA	Memphis Redbirds	30	19	19.1 IP	19.1 IP · 2.79 ERA · 37.2% K · 9.3% BB